KR101353696B1 - Surface-emitting laser device, surface-emitting laser array, optical scanning apparatus and image forming apparatus - Google Patents

Abstract

A surface-emitting laser element configured to emit laser light in a direction perpendicular to the substrate includes: a p-side electrode surrounding an emission area on an emission surface for emitting laser light; And a transparent dielectric film formed in the emission area on an external area outside the center of the emission area and having a reflectance lower than that of the center. The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

Description

SURFACE-EMITTING LASER DEVICE, SURFACE-EMITTING LASER ARRAY, OPTICAL SCANNING APPARATUS AND IMAGE FORMING APPARATUS

The present invention relates to a surface emitting laser element, a surface emitting laser array, an optical scanning device, and an image forming apparatus. More specifically, the present invention is a surface-emitting laser element and a surface-emitting laser array that emits laser light in a direction perpendicular to the substrate, an optical scanning device comprising the surface-emitting laser element or surface-emitting laser array, and the optical scanning An image forming apparatus including the apparatus.

The vertical cavity surface emitting laser device emits light in a direction perpendicular to the substrate, and the vertical cavity surface emitting laser device has a cross section that emits light in a direction parallel to the substrate. It is attracting attention recently because it is lower cost than the light emitting semiconductor laser element, lower power consumption, smaller size, and more suitable for two-dimensional devices.

Application fields of the surface-emitting laser element include a light source for an optical recording system in a printer (with an oscillation wavelength of 780 nm), a light source for recording in an optical disk device (with an oscillation wavelength of 1.3 µm or 850 nm), and an optical fiber. A light source for an optical transmission system such as a LAN (that is, a local area network) to be used (the oscillation wavelength is in the range of 1.3 µm or 1.5 µm) may be included. In addition, the surface-emitting laser element is expected to be applied to light sources for light transmission between boards, in boards, between chips of LSI (ie, Large Scale Integrated circuit), and in chips of LSI.

In these application fields, the light emitted from the surface-emitting laser element (hereinafter may also be referred to as "emission light") is often required to have a circular cross-sectional shape and a constant polarization direction.

In order to make the cross-sectional shape of the emitted light circular, it is necessary to control oscillation in the higher-order transverse mode. To this end, various attempts have been made, as disclosed in Japanese Patent Publication No. 3566902 (hereinafter referred to as Patent Document 1).

Further, as disclosed in Japanese Patent Publication No. 3955925 (hereinafter referred to as Patent Document 2), various attempts have been made to control the polarization direction of the emitted light.

In addition, as disclosed in Japanese Patent Laid-Open Publication No. 2007-201398 (hereinafter referred to as Patent Document 3) and Japanese Patent Laid-Open Publication No. 2004-289033 (hereinafter referred to as Patent Document 4), the oscillation control and polarization direction in the higher-order transverse mode It was examined to make the control compatible with.

However, in the methods disclosed in Patent Documents 1 and 2, it is difficult to make both the oscillation control of the higher-order transverse mode and the control of the polarization direction compatible. In addition, in the method disclosed in Patent Document 3, there is a fear that the operating life decreases due to an increase in the electrical resistance of the surface-emitting laser element or an increase in the current density. In addition, in the method disclosed in Patent Document 4, it is difficult to stabilize various characteristics of the surface-emitting laser element and control characteristics of the higher-order lateral mode.

Embodiments of the present invention may solve or reduce one or more of the problems described above.

More specifically, embodiments of the present invention may stabilize the polarization direction of the emitted light while controlling oscillation in the higher order lateral mode.

According to an embodiment of the present invention, there is provided a surface-emitting laser device that emits laser light in a direction perpendicular to the substrate,

A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And

Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.

/ RTI >

The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

According to another embodiment of the present invention, there is provided a surface-emitting laser array configured to emit a plurality of laser lights in a direction perpendicular to a substrate,

A plurality of surface emitting laser elements integrated on the substrate

/ RTI >

The surface-emitting laser element,

A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And

Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.

/ RTI >

The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

According to another embodiment of the present invention, there is provided an optical scanning device configured to scan a scan surface by laser light,

A light source including a surface-emitting laser element emitting laser light in a direction perpendicular to the substrate;

A deflection unit for deflecting laser light from the light source; And

Scanning optical system for condensing laser light deflected by the deflection unit

Including,

The surface-emitting laser element,

A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And

Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.

/ RTI >

The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

According to another embodiment of the present invention, there is provided an optical scanning device provided for scanning a scan surface by laser light,

A light source including a surface-emitting laser array that emits a plurality of laser lights in a direction perpendicular to the substrate;

A deflection unit for deflecting laser lights from the light source; And

Scanning optical system for condensing laser light deflected by the deflection unit

Including,

The surface-emitting laser array,

A plurality of surface emitting laser elements integrated on the substrate

/ RTI >

The surface-emitting laser element,

A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And

Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.

/ RTI >

The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

According to another embodiment of the invention, the image forming apparatus,

Image retainers; And

An optical scanning device configured to scan the image retainer with laser light modulated according to image information

Including,

The optical scanning device,

A light source including a surface-emitting laser element emitting laser light in a direction perpendicular to the substrate;

A deflection unit for deflecting laser light from the light source; And

Scanning optical system for condensing laser light deflected by the deflection unit

Including,

The surface-emitting laser element,

A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And

Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.

/ RTI >

The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

According to another embodiment of the invention, the image forming apparatus,

Image retainers; And

An optical scanning device configured to scan the image retainer with laser light modulated according to image information

Including,

The optical scanning device,

A light source including a surface-emitting laser array that emits a plurality of laser lights in a direction perpendicular to the substrate;

A deflection unit for deflecting laser lights from the light source; And

Scanning optical system for condensing laser light deflected by the deflection unit

Including,

The surface-emitting laser array,

A plurality of surface emitting laser elements integrated on the substrate

/ RTI >

The surface-emitting laser element,

A p-side electrode provided to surround the emission area on an emission surface for emitting the laser light; And

Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.

/ RTI >

The outer region in the exit area has shape anisotropy in two mutually perpendicular directions.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating schematic structure of the laser printer of the Example of this invention.
FIG. 2 is a schematic diagram illustrating the optical scanning device in FIG. 1.
3A is a first diagram for describing a surface-emitting laser element included in a light source.
FIG. 3B is a second view for explaining the surface-emitting laser element included in the light source, as viewed from a side different from that of FIG. 3A.
4A is a first view for explaining a substrate for a surface-emitting laser element.
FIG. 4B is a second view for explaining the substrate for a surface-emitting laser element seen from a side different from that of FIG. 4A.
5 is an enlarged view of the vicinity of the active layer.
6A is a first diagram for explaining the first manufacturing method for the surface-emitting laser element.
FIG. 6B is a second diagram for explaining the first manufacturing method for the surface-emitting laser element. FIG.
6C is a third view for explaining the first manufacturing method for the surface-emitting laser element.
FIG. 7A is a first diagram for describing the second manufacturing method for the surface-emitting laser element. FIG.
7B is a second diagram for describing the second manufacturing method for the surface-emitting laser element.
FIG. 8 is an enlarged view of the top surface of the mesa shown in FIG. 7B.
FIG. 9A is a first diagram for describing the third manufacturing method for the surface-emitting laser element. FIG.
FIG. 9B is a second diagram for describing the third manufacturing method for the surface-emitting laser element. FIG.
9C is a third view for explaining the third manufacturing method for the surface-emitting laser element.
FIG. 10 is an enlarged view of the upper surface of the mesa shown in FIG. 9C.
It is a figure explaining the 4th manufacturing method of a surface emitting laser element.
12 is a diagram for explaining the relationship between the suppression ratio SMSR of oscillation in the higher-order transverse mode and the area S of the current passage region.
FIG. 13 is a diagram for explaining the relationship between the polarization suppression ratio PMSR and the polarization angle θp.
It is a figure explaining the 1st modification of the surface emitting laser element.
It is a figure explaining the comparative example of a surface emitting laser element.
16 is a diagram illustrating a surface-emitting laser element used to calculate the oscillation mode distribution.
It is a figure explaining the relationship between the internal diameter L5 of a small area | region, and Q value in high-order transverse mode.
It is a figure for demonstrating the relationship between the internal diameter L5 of a small area | region, and the light confinement coefficient (Γ) of the horizontal direction of a basic horizontal mode.
It is a figure explaining the 2nd modified example of a surface emitting laser element.
20A is a first diagram for explaining a third modification of the surface-emitting laser element.
20B is a second diagram illustrating the third modification of the surface-emitting laser element.
FIG. 21A is a first diagram for describing the method for manufacturing the third modified example of the surface-emitting laser element. FIG.
FIG. 21B is a second diagram for describing the method for manufacturing the third modification example of the surface-emitting laser element. FIG.
21C is a third view for explaining the manufacturing method for the third modification to the surface-emitting laser element.
22A is a first diagram for describing the fourth modification of the surface-emitting laser element.
22B is a second diagram for describing the fourth modification of the surface-emitting laser element.
Fig. 23 is an enlarged view of the upper surface of the mesa in the manufacturing process of the surface-emitting laser element of the fourth modification.
24 is an enlarged view of an upper surface of a mesa of the surface-emitting laser element of the fourth modification.
It is a figure explaining the relationship between the presence or absence of the suppression structure of a higher-order lateral mode, and the suppression ratio (SMSR) of a higher-order lateral mode.
It is a figure explaining the relationship between R2 / R1 and polarization mode suppression ratio (PMSR).
27A is a first diagram for explaining the configuration of a low reflectance region.
27B is a second diagram for explaining the configuration of the low reflectance region.
27C is a third diagram for explaining the configuration of the low reflectance region.
27D is a fourth diagram for explaining the configuration of the low reflectance region.
27E is a fifth diagram for explaining the configuration of the low reflectance region.
27F is a sixth diagram for explaining the configuration of the low reflectance region.
28 is a diagram illustrating a surface emitting laser array.
FIG. 29 is a cross-sectional view taken along the line AA ′ of FIG. 28.
It is a figure explaining the schematic structure of color printing.

Embodiments of the present invention will be described with reference to the accompanying drawings in FIGS. 1 to 30. First, an embodiment of the present invention will be described based on FIGS. 1 to 18. 1 shows a schematic configuration of a laser printer 1000 as an image forming apparatus in an embodiment of the present invention.

The laser printer 1000 includes an optical scanning device 1010, a photosensitive drum 1030, a charger 1031, a developing roller 1032, a transfer charger 1033, a static elimination unit 1034, and a cleaning unit ( 1035, toner cartridge 1036, paper feed roller 1037, paper feed tray 1038, resist roller pair 1039, fuser rollers 1041, paper ejection rollers 1042. , A catch tray 1043, a communication control device 1050, and a printer control device 1060 that collectively controls these components. These components are housed in a fixed location in the printer package 1044.

The communication control device 1050 controls bidirectional communication with a host device (eg, including a personal computer) via a network.

The photosensitive drum 1030 is a cylindrical member, and a photosensitive layer is formed on the surface thereof. In more detail, the photosensitive drum 1030 has a scan surface. In addition, the photosensitive drum 1030 rotates in the direction of the arrow in FIG.

The charger 1031, the developing roller 1032, the transfer charger 1033, the antistatic unit 1034, and the cleaning unit 1035 are disposed near the surface of the photoconductive drum 1030. These components are arranged in the order of the charger 1031 → developing roller 1032 → transfer charger 1033 → antistatic unit 1034 → cleaning unit 1035 along the rotational direction of the photosensitive drum 1030. .

The charger 1031 charges the surface of the photosensitive drum 1030 uniformly.

The optical scanning device 1010 scans the surface of the photosensitive drum 1030 charged by the charger 1031 at a light beam modulated on the basis of the image information from the host device, and thus the image information on the surface of the photosensitive drum 1030. To form a latent image corresponding to. The latent image formed here moves toward the developing roller 1032 as the photosensitive drum 1030 rotates. The configuration of the optical scanning device 1010 will be described later.

The toner cartridge 1036 contains toner, which is provided to the developing roller 1032.

The developing roller 1032 attaches the toner provided from the toner cartridge 1036 to a latent image formed on the surface of the photoconductive drum 1030, thereby making the image visible. Here, the latent image to which the toner is attached (hereinafter, simply referred to as a "toner image") moves toward the transfer charger 1033 in accordance with the rotation of the photosensitive drum 1030.

The paper feed tray 1038 includes a recording sheet 1040. In the vicinity of the paper feed tray 1038, a paper feed roller 1037 is disposed. The paper feed roller 1037 extracts the sheet of the recording paper 1040 from the paper feed tray 1038, and the sheet of the recording paper 1040 (hereinafter referred to as "recording sheet 1040") is a pair of resist rollers 1039. To feed. The resist roller pair 1039 holds the recording paper sheet 1040 extracted by the paper feed roller 1037 for a while, and the recording sheet sheet 1040 is rotated by the photosensitive drum 1030, so that the photosensitive drum 1030 It feeds toward the gap between the transfer chargers 1033.

The transfer charger 1033 is applied with a reverse voltage to the voltage of the toner in order to electrically attract the toner on the surface of the photosensitive drum 1030. By the applied voltage, the toner image on the surface of the photosensitive drum 1030 is transferred to the recording paper sheet 1040. Here, the transferred recording paper sheet 1040 is sent to the fixing roller 1041.

The fixing roller 1041 applies heat and pressure to the recording paper sheet 1040, whereby the toner is firmly fixed on the recording paper sheet 1040. The recording paper sheet 1040 on which the toner is fixed is sent to the catch tray 1043 through the discharge roller 1042 and stacked on the catch tray 1043.

The antistatic unit 1034 discharges the surface of the photosensitive drum 1030.

The cleaning unit 1035 removes toner (i.e., residual toner) remaining on the surface of the photosensitive drum 1030. The surface of the photosensitive drum 1030 from which residual toner has been removed returns to the position opposite the charger 1031.

Next, the structure of the optical scanning apparatus 1010 is demonstrated.

This optical scanning device 1010 is, for example, as shown in Fig. 2, and includes a deflector side scanning lens 11a, an image scanning lens 11b, a polygon mirror 13, a light source 14, and a coupling lens. (15), the aperture plate 16, the anamorphic lens 17, the reflection mirror 18, and a scanning control device (not shown in FIG. 2). These components are set at fixed locations in the housing 30.

Hereinafter, for convenience, the direction corresponding to a main scanning direction is called "main scanning correspondence direction", and the direction corresponding to a vertical scanning direction is called "vertical scanning correspondence direction".

The coupling lens 15 makes the luminous flux emitted from the light source 14 into a substantially parallel luminous flux.

The aperture plate 16 includes an opening defining a beam diameter of the light beam passing through the coupling lens 15.

The anamorphic lens 17 condenses the light beam passing through the opening of the aperture plate 16, and forms an image in a vertical scanning-corresponding direction near the deflection reflective surface of the polygon mirror 13 by the reflection mirror 18.

The optical system arranged in the optical path between the light source 14 and the polygon mirror 13 is also called a before-deflector optical system. In the present embodiment, the deflection mechanism optical system includes a coupling lens 15, an aperture plate 16, an anamorphic lens 17, and a reflection mirror 18.

The polygon mirror 13 includes, for example, a six-sided mirror with an inscribed circle radius of 18 mm. Each side mirror of the six-sided mirror acts as a deflecting reflective surface. The polygon mirror 13 is rotated at constant speed around an axis parallel to the vertical scanning-correspondence direction to deflect the light beam from the reflection mirror 18.

The deflector side scanning lens 11a is arranged in the optical path of the light beam deflected by the polygon mirror 13.

The image scanning side scanning lens 11b is arrange | positioned at the optical path of the light beam which passed the deflector side scanning lens 11a. The light spot is formed on the surface of the photosensitive drum 1030 by irradiating the surface of the photosensitive drum 1030 with the light beam which passed the image surface side scanning lens 11b. The light spot moves in the longitudinal direction of the photosensitive drum 1030 in accordance with the rotation of the polygon mirror 13. In more detail, the light spot scans the surface of the photosensitive drum 1030. The moving direction of the light spot is the "main scanning direction". In addition, the rotation direction of the photosensitive drum 1030 is a "vertical scanning direction".

The optical system arranged in the optical path between the polygon mirror 13 and the photosensitive drum 1030 is called a scanning optical system. In this embodiment, the scanning optical system includes a deflector side scanning lens 11a and an image plane side scanning lens 11b. In addition, one or more turn-backs are provided in at least one of an optical path between the deflector side scanning lens 11a and the image scanning lens 11b and an optical path between the image scanning lens 11b and the photosensitive drum 1030. Mirrors may be arranged.

The light source 14 includes a surface emitting laser element 100, as shown by way of example in FIGS. 3A and 3B. In this specification, a laser oscillation direction is made into the Z-axis direction, and two directions orthogonal to each other in the surface perpendicular | vertical to a Z-axis direction are demonstrated as an X-axis direction and a Y-axis direction. 3A is a diagram showing a cross-sectional view parallel to the X-Z plane of the surface-emitting laser element 100. 3B is a diagram showing a cross-sectional view parallel to the Y-Z plane of the surface-emitting laser element 100.

The surface emitting laser element 100 emits a surface emitting laser having an oscillation wavelength of 780 nm. The surface emitting laser device 100 includes a substrate 101, a buffer layer 102, a lower semiconductor DBR (ie, a distributed Bragg reflector) 103, a lower spacer layer 104, an active layer 105, An upper semiconductor DBR 107, a contact layer 109, and the like.

The substrate 101 has a mirror polished surface. As shown in Fig. 4A, the normal direction of the mirror polished surface (also referred to as the main surface) is 15 degrees from the crystal orientation [1 0 0] toward the A direction of the crystal orientation [1 1 1] (that is, θ). = 15 degrees) sloped. The substrate 101 is an n-GaAs single crystal substrate and is a so-called inclined substrate. Here, as shown in FIG. 4B, the substrate 101 is arranged so that the crystal orientation [0-1 1] direction becomes the + X direction and the crystal orientation [0 1 -1] direction becomes the -X direction. .

In addition, by using the inclined substrate for the substrate 101, the polarization control action to stabilize the polarization direction in the X-axis direction is activated.

As shown in FIG. 3A, the buffer layer 102 includes n-GaAs and is stacked on the + Z side surface of the substrate 101.

A lower semiconductor DBR (103) is laminated on the + Z side of the buffer layer 102, and the low-refractive index layer including the _{n-AlAs, n-Al 0} .3 Ga 0 .7 40.5 of the high refractive index layer containing As It contains a pair. Referring to FIG. 5, composition inclined layers 20 having a thickness of 20 nm are provided between adjacent refractive index layers, in which the composition gradually changes from one composition to another in order to reduce electrical resistance. Each of the refractive index layers includes half of the adjacent layers, and is set to have an optical thickness of λ / 4 if the oscillation wavelength is λ. When the optical thickness is λ / 4, the actual thickness D of the layer is D = λ / 4n, where n is the refractive index of the medium of the layer.

The lower spacer layer 104, the non-doped (Al _{0 .1} Ga _{0 .9)} is laminated on the + Z side of the In _{0.5 0 .5} P and includes a lower semiconductor DBR (103) a.

The active layer 105 has a triple quantum well structure including three quantum well layers 105a and four barrier layers 105b and is stacked on the + Z side of the lower spacer layer 104 (FIG. 5). Each of the quantum well layers 105a includes a composition of GaInAsP that causes a compressive strain of 0.7% and has a band gap wavelength of about 780 nm. In addition, each of the barrier layers 105b includes a composition of GaInP that causes a compressive strain of 0.6%.

The upper spacer layer 106 is a layer containing a non-doped _{(Al 0 .1 Ga 0 .9)} 0.5 In 0 .5 P, is laminated on the + Z side of the active layer 105.

The portion including the lower spacer layer 104, the active layer 105, and the upper spacer layer 106 is called a resonator structure, and its thickness is set to be an optical thickness of one wavelength (see Fig. 5). The active layer 105 is provided in the middle of the resonator structure at a position corresponding to an antinode of the standing wave distribution of the electric field, so as to obtain a high stimulated emission probability.

An upper semiconductor DBR (107) is laminated on the + Z side of the upper spacer layer 106, comprising a p-Al _0.9 Ga _0.1 As low refractive index layer and a _{p-Al 0 .3 Ga 0 .7} As containing 23 pairs of high refractive index layers.

Between adjacent refractive index layers in the upper semiconductor DBR 107, in order to reduce the electrical resistance, composition gradient layers in which the composition gradually changes from one composition to another are provided. Each of the refractive index layers comprises half of the adjacent layers and is set to have an optical thickness of λ / 4.

In one of the low refractive index layers in the upper semiconductor DBR 107 is inserted an optional oxide layer 108 containing p-AlAs and having a thickness of 30 nm. The insertion position of the selective oxide layer 108 corresponds to the third node from the active layer 105 in the standing wave of the electric field.

The contact layer 109 includes p-GaAs and is stacked on the + Z side of the upper semiconductor DBR 107.

Such a structure including a plurality of semiconductor layers stacked on the substrate 101 is hereinafter referred to as a "laminated body".

Next, the manufacturing method of a surface emitting laser element is demonstrated briefly. The desired polarization direction (called desired polarization direction P) is taken as the X-axis direction.

(1) In Fig. 6A, a laminate is formed by crystal growth such as an organometallic chemical vapor deposition method (MOCVD method) or molecular beam epitaxy (MBE method).

As the group III raw material, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used. As group V raw materials, phosphine (PH ₃ ) and arsine (AsH ₃ ) are used. As raw materials for the p-type dopant, carbon tetrabromide (CBr ₄ ) and dimethylzinc (DMZn) are used. Hydrogen selenide is used as a raw material for the n-type dopant.

(2) On the surface of the laminate, a square resist pattern of 25 mu m in one side is formed.

(3) In the ECR etching method using Cl ₂ gas, a mesa structure (hereinafter referred to as "mesa" for convenience) of a square pillar is formed using the resist pattern as a photo mask. As shown in FIG. 6B, the bottom of the etch was set to be located in the lower spacer layer 104.

(4) The photo mask is removed (see FIG. 6B).

(5) The laminate is heat treated in water vapor. Accordingly, as shown in FIG. 6C, Al (ie, aluminum) in the selective oxide layer 108 is selectively oxidized at the outer periphery of the mesa, and the non-oxidized region 108b remains at the center of the mesa. More specifically, a so-called oxidative constriction structure is formed, which restricts the path of the drive current of the light emitting portion to only the center portion of the mesa. The non-oxidation region 108b is a current passing region (ie, current injection region). Thus, for example, an approximately square current passing region of 4 μm to 6 μm in width is formed.

(6) As shown in Fig. 7A, a protective layer 111 containing SiN is formed by chemical vapor deposition. The optical thickness of the protective layer 111 is set to be λ / 4. Specifically, since the refractive index n of SiN is 1.86 and the oscillation wavelength λ is 780 nm, the actual film thickness (same as λ / 4n) is set to about 105 nm.

(7) An etching mask (referred to as mask M) for forming an opening for p-side electrode contact is formed on an upper portion of the mesa serving as the emission surface of the laser light. As shown in FIG. 8 in which the mesa in FIGS. 7A and 7B is extracted and enlarged, the desired polarization direction P (X axis) is crossed across the periphery of the mesa, the periphery of the upper surface of the mesa, and the central portion of the upper surface of the mesa. The mask M is formed so as not to etch the two small regions (ie, the first small region and the second small region) facing each other in a direction parallel to the direction. More specifically, in Fig. 8, L1 is set to 5 mu m, L2 is set to 2 mu m, and L3 is set to 8 mu m.

(8) The protective layer 111 is etched by BHF (that is, Buffered Hydrofluoric acid) etching to form an opening of the p-side electrode contact.

(9) As shown in Figs. 9A and 9B, the mask M is removed. Hereinafter, the protective layer 111 remaining in the first small region is referred to as "transparent layer 11A", and the protective layer 111 remaining in the second small region is referred to as "transparent layer 111B".

(10) A square resist pattern of one side of 10 mu m is formed in a region serving as the light exit portion (i.e., the opening of the metal layer) on the upper side of the mesa, and vapor deposition of the p-side electrode material is performed. As the p-side electrode material, a multilayer film containing Cr / AuZn / Au or Ti / Pt / Au is used.

(11) As shown in Fig. 9C, the p-side electrode 113 is formed by applying a lift off technique to the electrode material deposited in the region (i.e., the emission region) to be the light exit portion. An area surrounded by the p-side electrode 113 is an emission area. FIG. 10 shows an enlarged view of the mesa extracted from FIG. 9C. The configuration of the emission area is a square whose one side is L4 (10 µm). In this embodiment, the transparent layer 111A and the transparent layer 111B exist in two small regions (the first small region and the second small region) as a transparent dielectric film containing SiN having an optical thickness of λ / 4. do. Accordingly, the reflectance of the two small regions (ie, the first small region and the second small region) is smaller than the reflectance of the central portion of the emission region.

(12) As shown in FIG. 11, the back surface of the substrate 101 is polished until it reaches a predetermined thickness (for example, about 100 µm), and then the n-side electrode 114 is formed. Here, the n-side electrode 114 is a multilayer film containing Au / Ni / Au.

(13) By annealing, ohmic contacts are formed between the p-side electrode 113 and the n-side electrode 114. Thus, the mesa becomes the light emitting portion.

(14) The chips are cut and separated from each other.

In the surface-emitting laser element 100 manufactured as described above, the relationship between the SMSR (i.e., Side Mode Suppression Ratio) of the high-order lateral mode when the light output is 2.0 mW and the area S of the current passing-through area is determined. Obtained. The result of this relationship is shown in FIG. 12 with a comparative example.

12 is a characteristic curve of the surface emitting laser element 100 of the Example of this invention, and B is the characteristic curve of the surface emitting laser element of the comparative example in which the emission area does not contain a dielectric film. In the case of reference numeral B, as the area of the current passing-through area is increased, the SMSR is significantly reduced because a higher-order transverse mode having a peak of light output tends to oscillate at the periphery of the emission area. On the other hand, in the case of reference numeral A, the SMSR is improved from 5 dB to 15 dB compared with the case of reference numeral B. FIG. In particular, an SMSR larger than about 25 dB is obtained in the range where the area S is 30 μm ² or less.

In general, the light output of the basic lateral mode is the largest near the center of the emission area, and tends to decrease as the position of the light output is dropped from the center. On the other hand, the light output of the higher order lateral mode is the largest at the periphery, and tends to decrease as the position of the light output approaches the center. In the present embodiment, the reflectances of the two small regions (i.e., the first small region and the second small region) set at the periphery of the emission area are set to be lower than the reflectance of the central portion, thereby lowering the reflectance for the basic transverse mode. It acts to lower the reflectance of the higher-order transverse mode without suppressing the oscillation.

In addition, with respect to the surface-emitting laser element 100, a relationship between PMSR (i.e., Polarizatoin Mode Suppression Ratio) and polarization angle [theta] p was obtained. 13 shows the result together with the comparative example. Here, the polarization mode suppression ratio means the ratio of the light intensity in the desired polarization direction to the light intensity in the direction perpendicular to the desired polarization direction. For example, the copier requires a polarization mode suppression ratio of about 20 dB. Here, the Y-axis direction represents the polarization angle (θp = 0 degrees), and the X-axis direction represents the polarization direction angle (θp = 90 degrees).

In Fig. 13, reference numeral A denotes the case of the surface-emitting laser element 100 of the embodiment of the present invention. Reference numeral C in FIG. 13 denotes a modification of the same surface-emitting laser element as when, for example, the surface-emitting laser element 100 rotates 90 degrees around the Z axis, as shown in FIG. 14. In addition, the code | symbol D in FIG. 13 includes the light emitting area in which one small area | region was set surrounding the center part of an emission area | region, as shown in FIG. 15, and the optical thickness formed in this small area | region is (lambda) / 4 The comparative example of the surface-emission laser element containing the phosphorus transparent dielectric film is shown.

As a result, in the case of reference numeral A, the polarization direction is stabilized in the X-axis direction. As a result, in the case of reference numeral C, the polarization direction is stabilized in the Y-axis direction. In all cases, the PMSR was about 5 dB higher than the case of reference D. On the other hand, in the case of reference numeral D, the polarization direction is stable in the X-axis direction, but the PMSR is lower than 10 dB, and sometimes the polarization direction is unstable.

As a factor in which the polarization stability is improved by forming a plurality of small regions in which a transparent dielectric film is formed, it is considered that the confinement action in two mutually perpendicular directions (the X-axis direction and the Y-axis direction) has shape anisotropy. In this embodiment, the light whose polarization direction coincides with the X-axis direction exerts a confinement action on the center of the emission area having a reflectance higher than the reflectance of the peripheral portion of the emission area, and the light polarization direction is higher than the light which coincides with the Y-axis direction. The oscillation threshold is lowered. As a result, it is thought that the polarization mode suppression ratio improved.

For example, as shown in Fig. 16, one ring-shaped small region 111 surrounding the central portion of the emission region in the circular emission region is set, and the small region 111 is transparent with an optical thickness of λ / 4. A dielectric film was formed, thereby constructing a surface emitting laser element (calculated surface emitting laser element). Regarding the surface-emitting laser element, the width L6 of the small region 111 was fixed at 3 μm, and the oscillation mode distribution was calculated while changing the inner diameter of the small region 111. In calculation, the diameter of the current passing-through area was set as 4.5 mu m. In addition, in Fig. 16, the same reference numerals are used for the same components as the surface-emitting laser element for convenience.

FIG. 17 shows the relationship between the inner diameter L5 of the small region 111 and the Q value in the higher-order transverse mode obtained from this calculation. According to this, it is noted that as the inner diameter L5 increases at 1 mu m, the Q value decreases substantially. This is because the portion of the high light intensity in the higher-order lateral mode overlaps with the small region 111, and oscillation in the higher-order lateral mode is suppressed. More specifically, by setting the inner diameter L5 to 5 micrometers-9 micrometers, oscillation of a higher-order lateral mode can be suppressed substantially.

18 shows the relationship between the inner diameter L5 of the small region 111 obtained from the above calculation and the light confinement coefficient Γ in the horizontal direction of the higher-order transverse mode. According to this, it is noted that the light confinement action in the lateral direction is strong when the inner diameter L5 is 5 μm or less, and that when the inner diameter L5 is larger than 5 μm, the light confinement action decreases as the inner diameter L5 increases. . This makes it possible to create a shape anisotropy in the light confinement action in the lateral direction by forming a plurality of small regions and providing a gap between the small regions. As a result, the polarization component in the direction of the strong light confinement action tends to oscillate more easily than the polarization component in the direction of the weak light confinement action, and the polarization direction can be controlled in the direction in which the light confinement action is strong.

As described above, according to the surface-emitting laser element 100 of the present embodiment, on the substrate 101, the buffer layer 102, the lower semiconductor DBR 103, the lower spacer layer 104, the active layer 105, and the upper portion The spacer layer 106, the upper semiconductor DBR 107, and the contact layer 109 are stacked. In addition, the surface-emitting laser element 100 includes a p-side electrode 113 provided to surround the emission area and an n-side electrode 114 on the substrate 101 side on the emission surface for emitting the laser light. . In addition, two small regions (ie, the first small region and the second small region) outside the central portion in the emission region are optically transparent dielectric films for lowering the reflectance of each small region than the reflectance of the central portion of the emission region. The transparent layer 111A and the transparent layer 111B are formed with the optical thickness of (lambda) / 4.

In this case, with the optically transparent film formed on the exit surface, the reflectance of the periphery of the exit area becomes relatively lower than the reflectance of the center of the exit area, without degrading the light output of the basic transverse mode, The rash can be suppressed.

In addition, the surface-emitting laser element 100 has a central portion of the emission area having a relatively high reflectance as a configuration having shape anisotropy in a direction perpendicular to each other, so that the light trapping action in the horizontal direction applied to the laser light is intentionally shaped. Anisotropy can be produced and the stability of a polarization direction can be improved.

That is, the oscillation of the higher-order transverse mode can be controlled and the polarization direction can be stabilized.

In addition, it is possible to control the higher-order transverse mode and the polarization direction without reducing the area of the current passage region. As a result, the resistance of the element and the current density of the current confinement region can be prevented from rising, thereby preventing deterioration of the element life.

In addition, the two small regions (ie, the first small region and the second small region) in the emission region face each other across the center of the emission region in a desired direction parallel to the polarization direction P. FIG. In this case, a dielectric film can be easily provided to each small region with high precision.

In addition, the board | substrate 101 is what is called a slanted board | substrate, and the opposing direction of a 1st small area | region and a 2nd small area | region is parallel to the inclination-axis direction (X-axis direction) of the main surface of the board | substrate 101. As shown in FIG. In this case, the polarization control action by using the inclined substrate can be added, and the stability of the polarization direction can be improved.

The side surface of the mesa is covered with the protective layer 111 of the dielectric film. In this case, destruction of the device caused by moisture absorption is suppressed, and long-term reliability can be improved.

According to the optical scanning device 1010, the light source 14 includes a surface emitting laser element 100. In this case, since laser light of a single basic transverse mode can be obtained, a circular and minute laser spot can be easily formed on the surface of the photoconductive drum 1030. In addition, since the polarization direction is stable, the optical scanning device 1010 is not affected by distortion of the light spot, variation in the light intensity, and the like. Therefore, in the basic optical system, it is possible to condense a circular, high-density, fine beam spot on the photosensitive drum 1030 and to form an image on the photosensitive drum 1030. Therefore, stable light scanning is possible.

According to the laser printer 1000 of this embodiment, since the laser printer 1000 includes the optical scanning device 1010, a high quality image is possible.

In the above-described embodiment, the case where the polarization control function of stabilizing the polarization direction in the X-axis direction by using the inclined substrate for the substrate 101 is described. When the polarization control action of stabilizing the polarization direction in the Y-axis direction is actuated, it is also possible to set the desired polarization direction P in the Y-axis direction, as shown in Fig. 14, and the first small region and the second small region. The direction in which the regions face each other can be set to be perpendicular to the main surface of the inclined axis direction (X-axis direction).

In addition, in this embodiment, the case where the protective layer 111 is SiN will be described, but the protective layer 111 is not limited to SiN. For example, SiN _x , SiO _x , TiO _x and SiON can also be used. By designing the film thickness according to the refractive index of each of the materials, a similar effect can be achieved.

In addition, in this embodiment, although the case where the 1st small area | region and the 2nd small area | region were symmetric about the axis which passes through the center of an emission area | region, and is parallel to a Y axis was demonstrated, this structure is not limited to this case. Various configurations are applicable as long as the first small region exists on one side of the axis passing through the center of the emission area and parallel to the Y axis, and the second small region exists on the other side of the axis.

In addition, in this embodiment, the case where the configuration of each of the small regions is a rectangle will be described, but the present configuration is not limited to the rectangle. The small regions may be of any shape, including elliptical, semicircular, as shown in FIG. 19.

In addition, in this embodiment, the case where the transparent layer 111A and the transparent layer 111B contain the same material as the material of the protective layer 111 was demonstrated, but the material of the transparent layer 111A and the transparent layer 111B is the same material. It is not limited.

In this embodiment, the case where the optical thicknesses of the transparent layers 111A and 111B are λ / 4 has been described, but the optical thicknesses of the transparent layers 111A and 111B are not limited to this case. For example, as illustrated in FIGS. 20A and 20B, the optical thicknesses of the transparent layer 111A and the transparent layer 111B may be 3λ / 4. Basically, as long as the optical thicknesses of the transparent layer 111A and the transparent layer 111B are odd multiples of [lambda] / 4, a lateral mode suppression effect similar to the surface-emitting laser element 100 in this embodiment can be obtained. 20A is a cross-sectional view when the surface emitting laser element 100A is cut into a plane parallel to the X-Z plane. 20B is a cross-sectional view when the surface emitting laser element 100A is cut into a plane parallel to the Y-Z plane.

In this case, as shown in Fig. 21A, for example, the p-side electrode of this embodiment is formed. Thereafter, as shown in FIG. 21B, for example, by using the chemical vapor deposition method, the protective layer 111 containing SiN is formed so as to have an optical thickness of 2λ / 4. More specifically, since the refractive index n of SiN was 1.86 and the oscillation wavelength was 780 nm, the actual film thickness (ie, 2λ / 4n) was set to about 210 nm. Next, as shown in FIG. 21C, the back surface of the substrate 101 was polished to a predetermined thickness (for example, about 100 μm), and then the n-side electrode 114 was formed.

At this time, the center part of the emission area was covered with the protective layer 111 having an optical thickness of 2λ / 4. In addition, the periphery of the emission region except for the two small regions (ie, the first small region and the second small region) was also covered with the protective layer 111 (dielectric film) having an optical thickness of 2λ / 4.

With respect to the surface-emitting laser element 100A, when the light output was 2.0 mW, the relationship between the suppression ratio SMSR of the higher-order transverse mode and the area of the current passing region was obtained, so that the area of the current passing through region was 30 m ² or less. A suppression ratio (SMSR) greater than 25 dB in the range was obtained.

In addition, the relationship between the polarization mode suppression ratio PMSR and the polarization angle θp is obtained for the surface emitting laser element 100A, and the polarization direction of the light emitted from the surface emitting laser element 100A is controlled in the X-axis direction. And a polarization mode suppression ratio (PMSR) as high as 20 dB was obtained.

In the surface emitting laser element 100A, the entire emission surface is covered with the protective layer 111 (that is, the dielectric film), so that oxidation or contamination of the emission surface can be prevented. In addition, since the center of the emission area is covered with the protective layer 111 (that is, the dielectric film) and its optical thickness is an even multiple of lambda / 2, the center of the emission area is the protection layer 111 without lowering the reflectance. The same optical properties were obtained as when not coated with).

More specifically, when the optical thickness of the portion where the reflectance is to be reduced is an odd multiple of λ / 4 and the optical thickness of the other portion is an even multiple of λ / 4, a lateral mode suppression effect similar to the present embodiment is obtained.

Further, in the present embodiment, the light source 14 may include the surface emitting laser element 100B as shown in, for example, FIGS. 22A and 22B instead of the surface emitting laser element 100.

The surface emitting laser element 100B emits a surface emitting laser having an oscillation wavelength of 780 nm, and includes a substrate 201, a buffer layer 202, a lower semiconductor DBR 203, a lower spacer layer 204, and an active layer 205. Top spacer layer 206, top semiconductor DBR 207, optional oxide layers 208a and 208b, and contact layer 209.

The substrate 201 is an inclined substrate similar to the substrate 101.

A lower semiconductor DBR (203) is laminated on the + Z side of the buffer layer 202, and a pair of 40.5 refractive index layer containing a low refractive index layer and the _{n-Al 0 .3 Ga 0 .7} As containing the n-AlAs It includes. Between adjacent refractive index layers, in order to reduce the electrical resistance, a composition gradient layer having a thickness of 20 nm is gradually changed from one composition to another. Further, each of the refractive index layers includes half of the adjacent composition gradient layers, and is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ.

The lower spacer layer 204 is laminated on the + Z side of the lower semiconductor DBR (203), comprises a non-doped _{(Al 0 .1 Ga 0 .9)} 0.5 In 0 .5 P.

The active layer 205 is stacked on the + Z side of the lower spacer layer 204 and is an active layer having a triple quantum well structure including three quantum well layers and four barrier layers. Each of the quantum well layers includes GaInAsP in a composition that causes a compressive strain of 0.7% and a band gap wavelength of about 780 nm. In addition, each of the barrier layers contains a composition of GaInP that causes a compressive strain of 0.6%.

The upper spacer layer 206 is stacked on the + Z side of the active layer 205 and includes undoped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P.

The portion including the lower spacer layer 204, the active layer 205, and the upper spacer layer 206 is also called a resonator structure and is set so that its thickness becomes an optical thickness of one wavelength. In addition, the active layer 205 is provided in the middle of the resonator structure corresponding to the breaking of the standing wave distribution of the electric field so as to obtain a high induced emission probability.

The upper semiconductor DBR 207 includes a first upper semiconductor DBR and a second upper semiconductor DBR (not shown in FIGS. 22A and 22B).

The first upper semiconductor DBR is laminated on the + Z side of the upper spacer layer _{(206), p- (Al 0.7} Ga 0.3) 0.5 and a low refractive index layer containing the _{In 0.5, p- (Al 0 .1} Ga 0. ₉₎ comprises a pair of high-refractive-index layer containing _0.5 in _{0 .5.} Between adjacent refractive index layers is provided a composition gradient layer which gradually changes from one composition to another in order to reduce the electrical resistance. Here, each of the refractive index layers includes half of the adjacent composition gradient layers and is set to have an optical thickness of λ / 4.

The second upper semiconductor DBR, the first upper portion is laminated on the + Z side of the semiconductor DBR, a high refractive index comprising a p-Al _0.9 Ga _0.1 As low refractive index layer and a _{p-Al 0 .3 Ga 0 .7} As containing It has 23 pairs of layers. Between adjacent refractive index layers is provided a composition gradient layer that gradually changes from one composition to another in order to reduce electrical resistance. Each of the refractive index layers comprises half of the adjacent composition gradient layers and is set to have an optical thickness of λ / 4.

In one of the low refractive index layers in the second upper semiconductor DBR, optional oxide layers 208a and 208b containing 30 nm thick p-AlAs are inserted. More specifically, a very thin layer, the first top semiconductor DBR, is located under the selective oxide layers 208a and 208b. The insertion positions of the selected oxide layers 208a and 208b correspond to the third node from the active layer 205 of the standing wave distribution of the electric field.

The contact layer 209 is laminated on the + Z side of the second upper semiconductor DBR and contains p-GaAs.

This in which a plurality of semiconductor layers are stacked on the substrate 201 is referred to hereinafter as "laminate B" for convenience.

Next, the manufacturing method of the surface emitting laser element 100B is demonstrated briefly. Here, the desired polarization direction P is taken as the X-axis direction.

(1) The laminate B is formed by crystal growth such as an organometallic chemical vapor deposition method (i.e., MOCVD method) and a molecular beam epitaxy method (i.e., MBE method).

(2) A resist pattern having one side of 25 µm is formed on the surface of the laminate B.

(3) A square pillar-shaped mesa is formed by an ECR etching method using Cl ₂ gas. Here, the bottom for etching is set to be in the lower spacer layer 204.

(4) The photo mask is removed.

(5) The laminate B is heat treated in water vapor. As a result, Al (i.e., aluminum) in the selective oxide layers 208a and 208b is selectively oxidized at the outer circumferential portion, and the non-oxidized region 208b surrounded by the oxide layer 208a of Al remains in the central portion of the mesa. More specifically, a so-called oxidative constriction structure is formed, which restricts the path of the driving current of the light emitting portion to the center portion of the mesa. The non-oxidation region 208b is a current passing region (ie, current injection region). Thus, for example, an approximately square current passing region of about 4 μm to 6 μm in width is formed.

(6) A protective layer 211 containing SiN is formed by chemical vapor deposition (ie, CVD). Here, the optical thickness of the protective layer 211 is set to be λ / 4. More specifically, since the refractive index n of SiN is 1.86 and the oscillation wavelength λ is 780 nm, the actual film thickness (ie, = λ / 4n) is set at about 105 nm.

(7) An etching mask (also referred to as mask M) is formed in order to form an opening of the p-side electrode contact on the upper surface of the mesa serving as the emission surface of the laser light. Here, as an example as shown in FIG. 23, only the mesa is extracted and enlarged to surround the mesa, the periphery of the upper surface of the mesa, and the center of the upper surface of the mesa, so that the minor axis direction has a desired polarization direction (P). The mask is formed so as not to etch an annular region that is parallel to (X-axis direction). More specifically, in Fig. 23, reference numeral R1 is 6 mu m, reference numeral R2 is 7 mu m, and reference numeral M1 is 10 mu m.

(8) The protective layer 211 is etched by BHF to form an opening of the p-side electrode contact.

(9) The mask M is removed.

(10) In the area | region used as the light output area | region (namely, opening part of a metal layer) of the upper part of a mesa, the square resist pattern of 10 micrometers on one side is formed, and p-side electrode material is deposited. As the p-side electrode material, a multilayer film containing Cr / AuZn / Au or Ti / Pt / Au is used.

(11) The p-side electrode 213 is formed by the lift-off method of removing unnecessary portions of the p-side electrode material deposited in the region (i.e., the emission region) to be the light output portion. 24 illustrates an enlarged view of only mesas extracted. An area surrounded by the p-side electrode 213 is an emission area. The configuration of the emission area is a square with one side M1 (10 mu m). In the annular region in the emission region, a transparent layer 211 exists as a transparent dielectric film of SiN having an optical thickness of? / 4. As a result, the reflectance of the annular region is lower than the reflectance of the central portion of the emission region.

(12) After the back surface of the substrate 201 is polished to a predetermined thickness (for example, about 100 µm), the n-side electrode 214 is formed. Here, the n-side electrode 214 is a multilayer film containing AuGe / Ni / Au.

(13) By annealing, ohmic contacts of the p-side electrode 213 and the n-side electrode 214 are formed. Thus, the mesa becomes the light emitting portion.

(14) Each chip is cut and separated.

In the surface-emitting laser element 100B produced as described above, in the emission region, the reflectance of the peripheral portion leaving the SiN film having a thickness of λ / 4n is lower than that of the central portion. In general, the light output in the basic lateral mode is the largest near the center of the emission area, and tends to decrease when dropped from the center. On the other hand, the light output of the higher order lateral mode is the largest at the periphery and tends to decrease as it approaches the center of the emission area. Therefore, in the surface emitting laser element 100B, it is possible to lower the reflectance of the higher-order lateral mode without lowering the reflectance of the basic lateral mode. More specifically, the action of suppressing the oscillation of the higher-order transverse mode works.

Fig. 25 shows light output between an element having a suppression structure of a higher order lateral mode similar to the surface-emitting laser element 100B (shown with reference numeral A), and an element having a suppression structure of a higher order lateral mode (shown with reference numeral B). When this is 1.4 mW, a comparison result of the suppression ratio of the higher-order transverse mode is shown. Here, the horizontal axis S is the area of the current passage region. In a device having no suppression structure of the higher order transverse mode, the SMSR is substantially lower because the higher order transverse mode with the peak of light output tends to oscillate at the periphery of the emission area. In contrast, in the device having the suppression structure of the higher order transverse mode, compared with the device having the control structure of the higher order transverse mode, the SMSR is improved by more than 10 dB, and the area S of the current passing-through area is more than 30 mm ² . In a small range, an improved SMSR of greater than 20 dB is obtained.

FIG. 26 also shows the relationship between R2 / R1 (where R1 is the inner diameter in a direction parallel to the polarization direction and R2 is the radius in the direction perpendicular to the polarization direction) and the polarization mode suppression ratio (ie, PMSR). . In FIG. 26, the point A shows the case where R1 = R2 = 5 micrometers. Point B represents a case where R1 = 5 µm and R2 = 6 µm. The point C shows the case where R1 = 5 micrometer and R2 = 7 micrometer. The point D represents R1 = 5 mu m, and the protective layer (low refractive index region) is divided into two.

Since the shape anisotropy of the gain is produced by using the inclined substrate, the polarization directions of all four structures face the X-axis direction regardless of the configuration of the low reflectance region. However, when comparing the polarization mode suppression ratios indicating the stability of polarization, the higher the ratio of the inner diameter in the direction perpendicular to the polarization direction (that is, R2) to the inner diameter in the direction parallel to the polarization direction (that is, R1), the higher the polarization. The result that the mode suppression ratio is improved is obtained.

As a factor which can obtain these results, it is considered that the light confinement action of two mutually perpendicular directions has shape anisotropy. At the points B and C, since the light confinement action to the center part of the polarization direction in the X-axis direction became stronger than the Y-axis direction, the oscillation threshold value of the light waves having the polarization component in the X-axis direction was lowered, thereby reducing the isotropic diameter. Polarization stability improved than the A point of the structure which has. Further, in the structure of point D that separates the low reflectance region into a plurality of portions, the polarization mode suppression ratio was the most improved among these points, which is similar to the surface emitting laser element 100.

Further, as shown in Figs. 27A to 27F, the configuration of the region of low reflectance is not limited to an elliptical annular shape including a major axis and a minor axis, and any configuration diagram such as a rectangle. A lateral mode suppression effect and a polarization control effect similar to the above-described embodiment can be obtained.

In addition, as an example, the light source 14 may include the surface emitting laser array 100C shown in FIG. 28 instead of the surface emitting laser element 100.

The surface-emitting laser array 100C includes a plurality of light emitting portions (21 in FIG. 28) disposed on a common substrate. In Fig. 28, the X-axis direction is the main scanning correspondence direction, and the Y-axis direction is the vertical scan correspondence direction. The plurality of light emitting parts are arranged at equal intervals when all the light emitting parts are orthographically projected along an imaginary line extending in the Y-axis direction. That is, 21 light emitting parts are arranged two-dimensionally. In addition, in this specification, the "light emitting part spacing" means the distance between the centers of two light emitting parts. In addition, the number of light emitting parts is not limited to 21.

Each of the light emitting portions has a structure similar to that of the surface-emitting laser element 100, as shown in FIG. 29, which is a cross-sectional view taken along the line A-A of FIG. In addition, the surface emitting laser array 100C may be manufactured by a method similar to that of the surface emitting laser device 100. Thus, it is possible to obtain a plurality of laser lights of a single basic transverse mode having a uniform polarization direction between the light emitting portions. Therefore, 21 small light spots that are circular and have a high light density can be formed on the photosensitive drum 1030 at the same time.

Further, in the surface emitting laser array 100C, the light emitting portions are equally spaced d2 when the light emitting portions are orthogonally projected along the imaginary line extending in the vertical direction, so that the timing of the lighting is adjusted to adjust the timing of the lighting. The surface emitting laser array 100C may be processed as in the case where the light emitting units are arranged at equal intervals in the vertical direction.

Further, for example, by setting the distance d2 at 2.65 占 퐉 and the magnification of the optical system of the optical scanning device 1010 twice, high density recording of 4800 dpi (that is, dot / inch) can be performed. Of course, by increasing the number of light emitting portions in the main scanning corresponding direction, an array arrangement in which the pitch d1 in the vertical scanning corresponding direction is narrowed to reduce the distance d2, and by reducing the magnification of the optical system, can be made more dense. And higher quality printing is possible. In addition, the recording interval in the main scanning correspondence direction can be easily controlled based on the timing of the lighting of the light emitting portion.

In this case, the laser printer 1000 can print without lowering the printing speed even if the recording dot density increases. In addition, in the case of the same recording dot density, the printing speed can be further increased.

Also, in this case, since the polarization directions of the light beams from the light emitting portions are stably matched, the laser printer 1000 can stably form a high quality image.

The trench between two adjacent light emitting portions is preferably at least 5 μm for electrical and spatial separation. If this groove is too narrow, it becomes difficult to control the etching at the time of manufacture. In addition, it is preferable that the size (length of one side) of mesa is 10 micrometers or more. If the size is too small, heat may be retained in the mesa, and the characteristics may deteriorate.

In addition, in the above-described embodiment, instead of the surface emitting laser element 100, a surface emitting laser array may be available in which light emitting portions similar to the surface emitting laser element 100 are aligned in one dimension.

Since the surface-emitting laser element 100 is integrated, the polarization direction can be stabilized while controlling the higher order transverse mode oscillation.

In addition, in this embodiment, the case where the normal direction of the main surface of the substrate is inclined 15 degrees from the crystal orientation [1 0 0] direction toward the crystal orientation [1 1 1] direction A will be described. It is not limited to. Any degree of inclination is possible if the normal direction of the substrate is inclined from one of the directions of the crystallographic orientation <1 1 0> toward one of the directions of the crystallographic orientation <1 1 1>.

In addition, in the above-described embodiment, the case where the oscillation wavelength of the light emitting portion is in the 780 nm band has been described, but the present embodiment is not limited to this case. Depending on the characteristics of the photosensitive member, the oscillation wavelength of the light emitting portion may be changed.

In addition, the surface-emitting laser elements described above can be used for applications other than image formation. In this case, the oscillation wavelength may be in a wavelength band including the 650 nm band, the 850 nm band, the 980 nm band, the 1.3 mu m and the 1.5 mu m bands, depending on the application. In this case, as the semiconductor material constituting the active layer, a mixed crystal semiconductor material according to the oscillation wavelength may be used. For example, an AlGaInP-based mixed crystal semiconductor material in the 650 nm band, an InGaAs-based mixed crystal semiconductor material in the 980 nm band, and a GaInNAs (Sb) -based mixed crystal semiconductor material in the 1.3 µm band and the 1.5 µm band may be used.

In addition, by selecting the material and configuration of the reflector according to the oscillation wavelength, a light emitting portion corresponding to an arbitrary oscillation wavelength can be formed. For example, a material other than an AlGaAs blend, such as an AlGaInP blend, may be used. Moreover, it is preferable that the low refractive index layer and the high refractive index layer are transparent with respect to an oscillation wavelength, and can enlarge the refractive index difference between them as much as possible.

In addition, in this embodiment, the case of the laser printer 1000 as the image forming apparatus has been described, but the image forming apparatus is not limited to the laser printer 1000.

For example, an image forming apparatus that emits laser light directly onto a medium (for example, paper sheet) that is colored by the laser light is also possible.

Moreover, the image forming apparatus using a silver salt film as an image retainer is also possible. In this case, a latent image is formed on the silver salt film by light scanning, and the latent image can be visualized by a process equivalent to the development process in a conventional silver halide photographic process. Next, a visible latent image can be transferred to the photo paper sheet by a process equivalent to printing in a conventional silver halide photographic process. Such an image forming apparatus can be embodied as an optical drawing apparatus or an optical drawing apparatus for drawing an image such as a computed tomography (CT) scan image.

Further, as shown in FIG. 30 as an example, a color print 2000 including a plurality of photosensitive drums can also be used.

This color print 2000 is a tandem multicolor printer which polymerizes four colors (black, cyan, magenta, yellow) to form a full color image. The color printer 2000 includes a black photosensitive drum K1, a charging device K2, a developing device K4, a cleaning unit K5, and a transfer device K6; Cyan photosensitive drum C1, charging device C2, developing device C4, cleaning unit C5, and transfer device C6; Magenta photosensitive drum M1, charging device M2, developing device M4, cleaning unit M5, and transfer device M6; And a yellow photosensitive drum Y1, a charging device Y2, a developing device Y4, a cleaning unit Y5, and a transfer device Y6. The color printer 2000 also includes an optical scanning device 2010, a transfer belt 2080, and a fixing unit 2030.

The photosensitive drums K1, C1, M1, Y1 rotate in the direction of the arrow of FIG. Around each photosensitive drum K1, C1, M1, Y1, along the direction of rotation, the charging devices K2, C2, M2, Y2, the developing devices K4, C4, M4, Y4, and cleaning Units K5, C5, M5 and Y5 are arranged. The charging devices K2, C2, M2, Y2 uniformly charge the surfaces of the corresponding photosensitive drums K1, C1, M1, Y1. The optical scanning device 2010 emits light to the surfaces of the photosensitive drums K1, C1, M1, and Y1 charged by the charging devices K2, C2, M2, and Y2, so that the respective photosensitive drums K1. , C1, M1, Y1) to form latent images. Corresponding developing devices K4, C4, M4, Y4 form toner images on the surfaces of the photosensitive drums K1, C1, M1, Y1. Further, the transfer apparatuses K4, C4, M4, Y4 transfer the toner images of the corresponding colors to the recording sheet on the transfer belt 2080. Finally, the fixing unit 2030 fixes the resulting image on the recording sheet.

The optical scanning device 2010 includes a color light source similar to the color light source of any one of the surface emitting laser elements 100, 100A, 100B and similar to the color light source of the surface emitting laser array 100C. In this way, the present optical scanning device can obtain an effect similar to that of the optical scanning device 1010.

Sometimes, the color print 2000 may generate a color deviation due to a manufacturing error or a position error of a part. Even in such a case, if the light source of the optical scanning device 2010 includes a surface emitting laser array similar to the surface emitting laser array 100C, the color change can be reduced by selecting the light emitting portion to be turned on.

As described above, the surface-emitting laser element of the present invention can stabilize the polarization direction while controlling oscillation in the higher-order transverse mode. In addition, the surface-emitting laser array of the present invention is suitable for stabilizing the polarization direction while controlling oscillation in the higher-order transverse mode. In addition, the optical scanning device of the present invention is suitable for stable optical scanning. Also, the image forming apparatus of the present invention is suitable for forming high quality images.

The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.

This application is based on Japanese Priority Patent Application No. 2008-302450, filed November 27, 2008, and Japanese Priority Patent Application No. 2009-122907, filed May 21, 2009, the entire contents of which are incorporated herein by reference. Used for

Claims (29)

A surface-emitting laser element configured to emit laser light in a direction perpendicular to the substrate,
A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And
Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.
/ RTI &gt;
The emission area has a shape corresponding to the inner surface of the p-side electrode,
The outer region in the emission region has shape anisotropy in two mutually perpendicular directions,
The outer region includes an annular region having an circular shape inside when viewed in the laser light-emitting direction, the annular region comprising a plurality of small regions divided into linear slits having a predetermined width; And the width of the linear slits is smaller than the inner diameter of the annular region. delete delete The method of claim 1, wherein the plurality of small regions includes a first small region and a second small region, wherein the first small region and the second small region face each other across the center of the emission region. Surface-emitting laser element. The method of claim 4, wherein the laser light is linearly polarized light,
The first small region and the second small region face each other in a direction parallel to the polarization direction of the laser light. delete The surface light emission of claim 4, wherein the normal direction of the main surface of the substrate is inclined from one of the directions of the crystal orientation <1 0 0> toward one of the directions of the crystal orientation <1 1 1>. Laser elements. delete The surface-emitting laser device according to claim 7, wherein the direction in which the first small region and the second small region face each other is parallel to the direction of the inclination axis of the main surface of the substrate. delete 8. The surface-emitting laser device according to claim 7, wherein the direction in which the first small region and the second small region face each other is perpendicular to the direction of the inclination axis of the main surface of the substrate. delete The surface-emitting laser device of claim 1, wherein an optical thickness of the transparent dielectric film is an odd multiple of 1/4 of an oscillation wavelength. The center of the emission area is covered with a second dielectric film,
And the optical thickness of the second dielectric film is an even multiple of 1/4 of the oscillation wavelength. 15. The surface-emitting laser device according to claim 14, wherein the second dielectric film covering the center of the emission area and the transparent dielectric film in the external area are made of the same material. The method of claim 1, wherein the outer region except for the plurality of small regions is covered with a third dielectric film,
The thickness of the third dielectric film is a surface-emitting laser device is an even multiple of 1/4 of the oscillation wavelength. delete 17. The surface-emitting laser element of claim 16, wherein the third dielectric film covering the outer region other than the plurality of small regions and the transparent dielectric film formed on the plurality of small regions comprise the same material. . delete The surface-emitting laser device of claim 1, wherein the transparent dielectric film formed on the plurality of small regions comprises one of films of SiN _x , SiO _x , TiO _x and SiON. delete The method of claim 1, wherein the exit surface is the upper surface of the mesa (mesa) structure,
The side surface of the mesa structure is coated with a fifth dielectric film. A surface-emitting laser array configured to emit a plurality of laser lights in a direction perpendicular to a substrate,
A plurality of surface emitting laser elements integrated on the substrate
/ RTI &gt;
The surface-emitting laser element,
A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And
Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.
/ RTI &gt;
The emission area has a shape corresponding to the inner surface of the p-side electrode,
The outer region in the emission region has shape anisotropy in two mutually perpendicular directions,
The outer region includes an annular region having an circular shape inside when viewed in the laser light-emitting direction, the annular region comprising a plurality of small regions divided into linear slits having a predetermined width; And the width of the linear slits is smaller than the inner diameter of the annular region. An optical scanning device configured to scan a scan surface by laser light, the optical scanning device comprising:
A light source including a surface-emitting laser element emitting laser light in a direction perpendicular to the substrate;
A deflection unit for deflecting laser light from the light source; And
Scanning optical system for condensing laser light deflected by the deflection unit
Lt; / RTI &gt;
The surface-emitting laser element,
A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And
Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.
/ RTI &gt;
The emission area has a shape corresponding to the inner surface of the p-side electrode,
The outer region in the emission region has shape anisotropy in two mutually perpendicular directions,
The outer region includes an annular region having an circular shape inside when viewed in the laser light-emitting direction, the annular region comprising a plurality of small regions divided into linear slits having a predetermined width; And the width of the linear slits is smaller than the inner diameter of the annular region. An optical scanning device configured to scan a scan surface by laser light, the optical scanning device comprising:
A light source including a surface-emitting laser array that emits a plurality of laser lights in a direction perpendicular to the substrate;
A deflection unit for deflecting laser lights from the light source; And
Scanning optical system for condensing laser light deflected by the deflection unit
Lt; / RTI &gt;
The surface-emitting laser array,
A plurality of surface emitting laser elements integrated on the substrate
/ RTI &gt;
The surface-emitting laser element,
A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And
Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.
/ RTI &gt;
The emission area has a shape corresponding to the inner surface of the p-side electrode,
The outer region in the emission region has shape anisotropy in two mutually perpendicular directions,
The outer region includes an annular region having an circular shape inside when viewed in the laser light-emitting direction, the annular region comprising a plurality of small regions divided into linear slits having a predetermined width; And the width of the linear slits is smaller than the inner diameter of the annular region. An image forming apparatus comprising:
Image retainers; And
An optical scanning device configured to scan the image retainer with laser light modulated according to image information
Lt; / RTI &gt;
The optical scanning device,
A light source including a surface-emitting laser element emitting laser light in a direction perpendicular to the substrate;
A deflection unit for deflecting laser light from the light source; And
Scanning optical system for condensing laser light deflected by the deflection unit
Lt; / RTI &gt;
The surface-emitting laser element,
A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And
Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.
/ RTI &gt;
The emission area has a shape corresponding to the inner surface of the p-side electrode,
The outer region in the emission region has shape anisotropy in two mutually perpendicular directions,
The outer region includes an annular region having an circular shape inside when viewed in the laser light-emitting direction, the annular region comprising a plurality of small regions divided into linear slits having a predetermined width; And the width of the straight slits is smaller than the inner diameter of the annular area. An image forming apparatus comprising:
Image retainers; And
An optical scanning device configured to scan the image retainer with laser light modulated according to image information
Lt; / RTI &gt;
The optical scanning device,
A light source including a surface-emitting laser array that emits laser light in a direction perpendicular to the substrate;
A deflection unit for deflecting laser light from the light source; And
Scanning optical system for condensing laser light deflected by the deflection unit
Lt; / RTI &gt;
The surface-emitting laser array,
A plurality of surface emitting laser elements integrated on the substrate
/ RTI &gt;
The surface-emitting laser element,
A p-side electrode surrounding the emission area on an emission surface for emitting laser light; And
Within the emission area, a transparent dielectric film is formed on an external area outside the center of the emission area to make the reflectance lower than that of the center area.
/ RTI &gt;
The emission area has a shape corresponding to the inner surface of the p-side electrode,
The outer region in the emission region has shape anisotropy in two mutually perpendicular directions,
The outer region includes an annular region having an circular shape inside when viewed in the laser light-emitting direction, the annular region comprising a plurality of small regions divided into linear slits having a predetermined width; And the width of the straight slits is smaller than the inner diameter of the annular area. 27. An image forming apparatus according to claim 26, wherein said image information is multicolor image information. An image forming apparatus according to claim 27, wherein said image information is multicolor image information.

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